Asia-Pacific markets open lower after gains on Wall Street; Japan and South Korea data in focus

Asia-Pacific markets opened lower on Wednesday, despite gains on Wall Street ahead of the U.S. August consumer inflation report due Wednesday.

Traders in Asia parsed key economic data from Japan and South Korea. South Korea reported that unemployment fell to 2.4% in August, the lowest level since 1999, when the data series commenced, according to Statistics Korea.

The Reuters Tankan survey, a monthly poll that tracks business sentiment in Japan, showed that business confidence in big manufacturers dipped to plus 4 in September, a seven-month low, from plus 10 in August. The sentiment for non-manufacturers declined for a third consecutive month to plus 23, from plus 24.

Republican presidential nominee Donald Trump and Democratic Vice President Kamala Harris are set to meet for the first time for the presidential debate in Asia's morning hours.

Separately, the Federal Trade Commission has warned Japanese retail company Seven & i that it may probe its potential deal with Canada's Alimentation Couche-Tard, Reuters reported, citing two sources.

Seven & i recently rejected Couch-Tard's proposal, partially over U.S. antitrust concerns. The company's shares fell nearly 2% Wednesday morning.

Chipmaking powerhouse Taiwan Semiconductor Manufacturing Corp announced its August revenue of 250.87 billion New Taiwan Dollars ($7.8 billion), increasing 33% year-on-year while dropping 2.4% from July. 

Japan's Nikkei 225 was 0.7% down and the broad-based Topix was 0.86% lower.

South Korea's Kospi slipped 0.20%, while the small-cap Kosdaq rose 1.61%.

Australia's S&P/ASX 200 was marginally higher.

Hong Kong Hang Seng index futures were at 17,072, lower than the HSI's last close of 17,190.

Overnight in the U.S., stocks wavered through Tuesday's trading session, with two of the three major U.S. indexes ending in the green, as traders are betting that a widely anticipated interest rate cut at the Federal Reserve September meeting would assuage concerns over a weakening economy.

The broad-based S&P 500 advanced 0.45% and the Nasdaq Composite climbed 0.84%, while the Dow Jones Industrial Average dipped 0.23%.

—CNBC's Brian Evans and Pia Singh contributed to this report.